The present invention generally relates to splined joints and, more particularly, to grease seal cups to retain lubrication for life extension in existing splined joints.
Splined joints are used in many devices for transmitting torque between two components, such as a motor drive shaft and compressor shaft. Generally, a splined joint includes a series of internal splines formed on one of the components engaging a series of external splines formed on the other of the two components. Typically, a splined joint is assembled by positioning the two components end-to-end lengthwise so that the internal splines are circumferentially aligned with the spaces between the external splines and then sliding the components axially into overlapping engagement so that the two sets of splines become enmeshed with one another.
A lubricating material, such as grease, may be provided at the interface of the internal and external splines to reduce component wear. During component operation, the lubricating material tends to be removed from the spline interface due to centrifugal force. Additionally, some splined joints are exposed to materials, such as hot hydraulic fluid, which also tend to remove the grease that is intended to lubricate the splines. Without lubrication, the splines wear out prematurely and limit the component service life. For some applications, the loss of spline joint lubrication has limited component service life to ¼-life.
U.S. Pat. No. 4,281,942 provides a lubrication system for a spline connection. The described system comprises a split ring at one end of the spline connection and a supply of oil at the other end. During operation, centrifugal force pushes the two halves of the split ring apart, allowing the oil to flow through the spline connection and out through the split ring. A quad o-ring around the circumference of the split ring pulls the two halves together when the shaft is stationary, closing off the oil path. Although the disclosed system may provide lubrication for a spline connection, the added weight of the heavy metal split ring may not be suitable for some existing applications. For example, applications including a Scotch yoke design require the weight balance to be maintained and the incorporation of the heavy split ring may necessitate a total redesign. Additionally, this lubrication system does not sufficiently reduce lubrication loss due to hot hydraulic fluid exposure.
Japanese Patent No. JP11180259 provides a grease cup for a connecting shaft. The cup comprises a rigid washer positioned between a shaft and a rotary lever. The rigid washer is bent upward during assembly to suppress the outflow of grease from the area between the shaft and the lever and to prevent the inflow of water. Although the described grease cup may be used to reduce grease loss from the joint between a shaft and a lever, it may not have the symmetry necessary for use in a splined joint between two high-speed rotating shafts. Additionally, because the described cup is formed during installation by bending the washer, it may not be useful for applications requiring an easy to install pre-fabricated component.
As can be seen, there is a need for improved mechanisms to retain splined joint lubrication. A lightweight apparatus that can maintain the weight balance of an existing system is needed. Additionally, an apparatus is needed that is pre-fabricated and easy to install.